Sophisticated wireless data communications devices, systems and networks, such as cellular telephones and wireless LAN transceivers, are in widespread use worldwide. There is increasing need for higher data rates and the support of an increased number of users and data traffic, and these networks employ complex signal waveforms and advanced radio frequency capabilities such as multiple-input multiple-output (MIMO) signal coding for achieving higher bandwidths. Further, the rapidly decreasing physical size and power consumption of these devices and systems cause them to become ever more highly integrated, with internal antennas and fully sealed construction. All of these techniques, however, increase the complexity of the wireless devices. Manufacturers, vendors and users therefore have a greater need for better testing of such systems.
Unfortunately, the complexity of wireless data communication devices and systems makes them particularly problematic to test due to the difficulty of accessing their internally integrated antennas, isolating them from external interference, and controlling the coupling between the wireless device and the test equipment. Actual open-air RF environments contain high levels of uncontrollable noise and interference, and also present time-varying and unpredictable channel statistics. However, external noise and interference have significant impact on device performance. The lack of controllability and repeatability also makes it difficult or impossible to automate the testing of such wireless systems. Therefore, it is very attractive to manufacturers and users to test these devices in a repeatable fashion by excluding the interference and variability of real RF environments and also controlling the degree of coupling between the wireless device and the test equipment. This also enables the tests to be conducted in an automated fashion, or by personnel not highly skilled in RF channel characteristics.
Traditional methods of isolating and coupling to wireless communications devices include: anechoic and reverberation chambers; shielded enclosures of various sizes; cabled connection to device antenna connectors or antennas; use of antenna ranges; and operation in open air environments. All of these methods exhibit one or more deficiencies when considering the requirements of modern MIMO wireless devices. Anechoic and reverberation chambers are very expensive, bulky and fixed at one location due to their large size and weight. Shielded enclosures offer limited portability but are still relatively expensive and heavy, and suffer from repeatability issues. Further, small shielded enclosures present many problems when dealing with MIMO systems. Cabled connections to the wireless device under test are simple and offer very high repeatability and low cost, but are unfortunately impractical or impossible with modern highly integrated compact devices such as cellular telephones. Outdoor antenna ranges are expensive and difficult to find, due to their real estate requirements, and further have problems when dealing with MIMO transmission. Open air environments are highly variable, nearly impossible to reproduce, and present significant challenges with repeatability and controllability. All of these problems are exacerbated when considering the trend in modern wireless devices of incorporating multiple antennas that are integrated into the device, non-detachable, and with a high degree of impact on device performance.
The known methods in the field of wireless device testing therefore suffers from serious shortcomings with regard to isolating and coupling to a device under test. There is hence a need for improved wireless data communication test systems and methods. A system that is inexpensive, highly portable, and capable of handling devices with integrated non-detachable antennas is desirable. It is preferable for such a system to provide shielding of the device under test from external interference, as well as coupling of radio frequency signals between the device under test and the test equipment. Further, such a system should allow repeatable coupling to device antennas without special jigs or expensive fittings, even though the device antennas may be located internally and not visible in normal operation. Finally, the system should present simplified use and operation to permit less skilled personnel to conduct testing of advanced wireless devices, and should also accommodate wireless devices of different sizes and shapes without modification.